The present invention relates to a high-definition television receiver for reproducing a television image from high-definition television signals, and furthermore from, quasi-high-definition television signals which have been converted from television signals of a conventional standard television system.
The high-definition television (HDTV) system has been developed to incorporate a wide screen of greater size for a fine reproduction picture and thus to provide improved visual effects of vividness and presentation which cannot be obtained on a conventional standard television receiver. Nippon Hoso Kyokai (NHK) offers its high-definition television system featuring the aspect ratio (width to height) of a television screen of 5:3 or 16:9 (as will be described hereinafter with a ratio of 16:9) and the 1125 scanning lines, as compared to the 4:3 aspect ratio and 525 lines of the conventional standard television system.
This type of high-definition television system is briefly depicted in the report of T. Fujio, "High-definition Wide-screen Television System for the Future", IEEE Trans., vol. BC-26, No. 4, p. 113 (1980).
Also, there has been proposed a method in which a television image derived from television signals of the conventional standard television system (e.g. the N.T.S.C. system) can be received with equal success on a high-definition television receiver which is substantially designed for reproduction of high-definition television pictures upon receipt of high-definition television signals.
FIG. 1 shows the schematic arrangement of a circuit provided in a device for reproducing an image from television signals of the conventional standard television system with a prior art high-definition television receiver. A television signal of the conventional standard television system is input through a conventional standard television signal input port 11 and then converted into a quasi-high-definition television signal by a signal converter 12 as the scanning lines are doubled from 525 to 1050 by scanning conversion. There is a switch circuit 14 which selectively transmits either the converted television signal or a signal of the high-definition television system supplied through an input port 13 to a high-definition television display 15 for reproducing a televised image on its wide screen. FIG. 2 illustrates television images reproduced on the high-definition television display 15 from the quasi-high-definition signals converted from the conventional standard television signals. As shown in FIG. 2, the numeral 21 is a 16:9 aspect ratio screen of the high-definition television display while 22 and 23 represent areas of a 4:3 aspect ratio for reproduction of pictures from the quasi-high-definition television signals converted from the conventional standard television signals. There is a difference in aspect ratio between the two television systems and thus, a screen of a particular size will not correspond to both of the distinctly sized pictures of their respective systems. In the prior art, a high-definition television receiver is alternatively arranged so that a reproduction picture of the conventional standard television system can correspond to the high-definition television screen either in frame height, as shown in FIG. 2-a or in frame width, as shown in FIG. 2-b.
Accordingly as shown in FIG. 2-a, this type of a high-definition television receiver permits a reproduction picture 22 of the conventional standard television system to appear in a smaller size such that the high-definition television display screen 21 has non-scanned areas on both left and right ends (represented by oblique lines) thus being shortened in effective area. On the other hand, a high-definition television receiver shown in FIG. 2-b permits the same to appear in over-sized fashion with its upper and lower end portions situated off the screen 21 and thus to become imperfect in visual image.